Absorbent microbiocidal fabric and product

ABSTRACT

An absorbent, highly wettable, bioactive, dyed fabric useful as a surgical drape, dressing or the like is disclosed composed of a non-cellulosic substrate having incorporated on it a non-leachable bioactive silicone quaternary amine, a hydrophilic organosilicone terpolymer and a direct dye. The fabric is used to isolate a surgical incision site and provides an absorbent antimicrobial field to destroy migrating and cross-contaminating bacteria, fungi and algae. Procedures for producing the fabric are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of my earlier applicationSer. No. 310,416 filed Oct. 9, 1981.

This invention relates to a process for dyeing absorbent fabric suitablefor use as a surgical drape, dressing or the like which is used toisolate a surgical incision site and at the same time provides anabsorbent antimicrobial field which becomes substantive on the fabricand services to destroy migrating and cross-contaminating bacteria,fungi and algae. Such fabric is colored, highly wettable, bioactive andserves to lower the amount of microbial contamination while lowering therisk of post-operative infection.

BACKGROUND OF THE INVENTION

A need exists for a dyed surgical drape, bandage or like product thatkills bacteria but is itself non-toxic, that provides permanentantimicrobial capacity yet the antimicrobial agent itself is notextracted from the fabric in use and that maintains its effectivenessover a period of time but is not inhibited by sterilization, storage orhandling.

A particularly useful antimicrobial agent is Q9-5700, an antimicrobialagent available from Dow Corning Corporation of Midland, Mich. Thematerial is a silicone quaternary amine, chemically3-(trimethoxysilyl)-propyloctadecyl dimethyl ammonium chloride. Thismaterial has been used to protect textiles and inhibit odor-causingbacteria and fungi which contamination may result in odor problems,discoloration and deterioration of these textiles. Application of thistype of silicone quaternary amine onto the surface of textiles has beenfound to inhibit the growth of microorganisms and to aid in the controlof the above-mentioned problems. As such it is authorized by theEnvironmental Protection Agency of the United States Government for useon textile surfaces (EPA No. 34292-1) and it has also been accepted bythe Food and Drug Administration of the U.S. Government for use inmedical devices for use association with humans and animals.

Surgical drapes and like materials are typically made of non-woventextiles or other non-woven type materials, however when such siliconequaternary amines are applied to a non-woven substrate it was found thatthe substrate was rendered hydrophobic, thus aqueous-based fluids,including normal body fluids, were repelled by such a coated substrate.Further difficulties were encountered in maintaining the integrity ofthe silicone quaternary amine in or on the substrate and preventing itfrom leaching away from the substrate and possibly contaminatingpatient's surface area surrounding the site of the surgical procedureand even possibly contaminating the surgical opening itself.

The requirements for a successful medical fabric or substrate includethe following:

1. The substrate must be bioactive, that is it much achieve a 95% orbetter bactericidal effect within one hour. In other words, the materialis bacteriocidal and not merely bacteriostatic as is the case with thewearing apparel.

2. The bioactive/bactericidal material must remain on the substrate andnot be leached from the substrate, but if leaching occurs it must bevirtually undetectable, i.e. only less than 0.2 parts per million (0.2ppm) from a 1.2 inch×1.2 inch swatch according to test procedures,described in more detail below. Non-leachability or substantialnon-leachability is a factor of the fabric sample or swatch size beingtested.

3. The leachate removed from a sample of the medical substrate must notexhibit cytotoxicity to cells. This includes not only the antimicrobialagent itself but also other finishes, colorants or the like that mayalso be applied to the substrate. A typical testing procedure includesadding a standardized cell culture to a leachate recovered from apredetermined sample size of the substrate being tested, incubating theculture plus leachate and observing the culture for either cell death ormorphological change to the cells in the culture.

4. The medical substrate must be non-flammable in accordance withstandard CS-191-53.

5. The medical substrate must conform to the anti-static requirements oftest NFPA 56-A.

6. The substrate itself must be absorptive of normal body fluids, suchas physiological saline, and blood.

7. The dye must stay on the substrate and be fixed thereto thus freefrom crocking and water bleeding.

In addition to providing a medical substrate that satisfies all of theabove-listed performance requirements it is also desirable from acommercial viewpoint, to color or dye the substrate an aestheticallypleasing color, for example blue or green, the colors of choice forequipment used in surgical procedures. Simply adding a tinctorial amountof the desired dye to a pad bath containing the bioactive compound doesnot provide the desired result--it appears that the strongly anionicnature of direct dyestuffs, commonly used to color paper and othercellulosic products, prevents the preparation of finishing bathscontaining both the strongly cationic bioactive compound and the anionicdirect dyes. It is more efficient to apply the required finish,including color, to the cellulosic substrate in a single finishing stepor bath than to use multiple baths, steps and drying operations.

It has been a continuing difficulty in the art to identify anappropriate finishing agent or group of agents that will inhibit thehydrophobicity imparted to the substrate by the silicone quaternaryamine antimicrobial agent and provide a substrate conforming to theseven requirements identified above. Virtually all detergents commonlyused as fabric softeners are leachable from a non-woven substrate andtend to lyse cells to at least some extent. For example, to besuccessfully used organic non-ionic surfactants may require asubstantial amount of the surfactant on the substrate, for instance from5 to 15%, calculated on the weight of the fabric.

Another difficulty encountered is in the selection of an appropriatesubstrate is that the silicone quaternary amine-type antimicrobialcompounds do not readily adhere to polyester substrates and that as suchthe resulting product does not conform to the maximum leachabilityrequirements, as stated above. Accordingly cellulosic substrates arepreferred, although minor amounts of polyester in a cellulosic/polyesterblend may be tolerated.

Suitable finishing agents, antimicrobial agents and operationalparameters are disclosed in my copending application Ser. No. 310,414filed on even date herewith, the disclosure of which is herebyincorporated by reference.

BRIEF DESCRIPTION OF THE DRAWING

The attached drawing schematically represents the process of myinvention.

DETAILED DESCRIPTION OF THE INVENTION

I have found, and hereby disclose, a process for preparing a dyed,absorptive, bacteriostatic non-woven medical substrate in which asolution of a specific silicone quaternary amine is applied with adirect dye and a member of a specific class of rewetting agents whichact as hydrophilic coupling agents to secure the quaternaryamine+rewetting agent+direct dye to the substrate. The rewetting agentimproves the compatibility of anionic direct dye with the cationicquaternary amine antimicrobial agent and imparts the necessary waterabsorptive qualities in the product yet becomes substantive(non-leachable) on the fabric meeting the bioactivity, leachability,cytotoxicity, non-flammability, anti-static and absorptive propertiesenumerated above.

According to the procedure of this invention a tinctorial amount of oneor more direct dyes is slurried with an organosilicone terpolymer and tothe resulting solution the desired amount of bioactive silyl quaternaryamine is added. Typically the amounts of each of the three ingredientswill be up to about 1 percent calculated on the dry weight basis of thefabric.

I have found that an aqueous-based solution preferably containing: (1)from about 0.2 to about 1.1% of 3-(trimethoxysilyl)-propyloctadecyldimethyl ammonium chloride as the microbiocide, together with (2) fromabout 0.5 to 1.5 weight % of an epoxypolyoxyalkylene modifiedorganosilicone as a hydrophilic coupling agent, sometimes referred to asa "rewetter" herein, and (3) a tinctorial amount up to about 1% of oneor more direct dyes when applied to a suitable non-wovencellulosic-based substrate will produce a colored, waxy,water-insoluble, bioactive, absorbent, wettable finish on the materialwhich retains the dye, bioactive material and the hydrophilic couplingagent yet conforms to the necessary cytotoxicity, non-flammability andanti-static requirements listed above.

While not wishing to be bound by any particular theory it appears that acombination of the three materials produces a type of cross-linkedmatrix reactivity bonded to the fiber of the substrate. The presence ofthe epoxy-polyoxyalkylene organosilicone material in the treatment bathserves not only to provide the necessary rewetting/absorptive qualitiesfor the finished product but also prevents the silicone quaternary aminebioactive material from complexing and becoming gelled during processingoperations thus extending shelf life and reducing the loss ofmicrobiocide from the solution. The aqueous-based solutions used in theprocess of my invention are typically applied by padding onto a suitablenon-woven substrate although other application procedures may be used.

Suitable non-woven substrates are used in the process of my inventionare essentially all cellulosic in nature and include paper, cotton,rayon and possibly wool, but not the substrates composed essentiallyentirely of an acrylic, polyester or nylon fiber. The preferredsubstrate is a dry laid spray bonded paper toweling material which isbonded with acrylic resins and contains about 80-85% by weight paper(cellulose) with 15-20% by weight acrylic resin binder. This material isavailable from the Fort Howard Paper Company under their styledesignation E-34. Also suitable is a wet-laid paper that is creped andprint bonded and which is composed of about 90% by weight cellulose andabout 10% by weight acrylic binder. Such materials include the ScottHi-Loft materials under style designations 3051 and 3055 available fromthe Scott Paper Company. Non-woven substrates containing significantlyless than about 80% cellulosic content are not preferred.

The procedure of my invention will now be described with reference tothe attached drawing. As shown in the figure a non-woven substrate isdirected from a supply reel through a pad bath (the content of which areexplained below) and passed through a nip roll to achieve an overall wetpickup (wpu) of between about 75 and 125% calculated on the weight ofthe non-woven substrate. Preferably the wet pickup is in the range ofabout 85 to about 115% also expressed on the weight of the substrate.Next the impregnated substrate is passed through a stack of steam cansmaintained at a suitable temperature so that dry/cure occurs at betweenabout 280° and 360° F. As the wet material is passed over the series ofsteam cans the lower stack of cans tends to remove the water and dry thematerial while the upper stack of cans adds additional heat and curesthe material setting the applied components to the substrate. Preferablythe material is subjected to a temperature in the range of 280°-300° F.for at least about 5 seconds. The dried, finished product is then ledaway from the stack of steam cans, rolled and stored wrapped in plasticbags or the like.

The preferred silicone quaternary amine bioactive material is3-(trimethoxysilyl)-propyloctadecyl-dimethyl ammonium chloride which isdescribed in U.S. Pat. No. 3,730,701, the disclosure of which is herebyincorporated by reference. A class of suitable bioactive silylquaternary amine compounds have the formula: ##STR1## in which R is aC₁₁₋₂₂ alkyl group and R¹ is chlorine or bromine. The preferred siliconequaternary amine is 3-(trimethoxysilyl)-propyloctadecyl dimethylammonium chloride and is available as a 42% active solids in methanolfrom Dow Corning Corporation of Midland, Mich. under the designationDC-5700 (formerly q9-5700). This material is well accepted in commerceand has been approved not only as a bacteriostatic textile treatment butalso as a bactericidal component for medical device/non-drugapplications.

As the hydrophilic coupling agent there is used a member of the class ofthe epoxy-polyoxyalkylene modified organosilicones described in U.S.Pat. No. 4,184,004, the disclosure of which is incorporated herein byreference. The preferred material is available in commerce from UnionCarbide Corporation and is believed to respond to the following generalstructure:

    MD.sub.x D'.sub.y D".sub.z M

in which the units are end-capping units and are identical to eachother, the various "D" and "M" units having the following configuration:##STR2## as disclosed in U.S. Pat. No. 4,184,004. In the above formula Rrepresents either hydrogen or methyl and the total of a+b is believed tobe from 5 to 200. The average values of x, y and z are as follows:

x=: 10 to 50,000;

y=: 1 to x;

z=: 1 to 0.5x provided that,

y+z≦0.75x

preferably:

x=: 25 to 1,000;

y=: 1 to 0.5x provided that,

z=: 1 to 0.25x and

y+z≦0.5x

most preferably:

x=: 50 to 300

y=: 1 to 0.25x

x=: 1 to 0.15 x, provided that

y+z≦0.25 x

as disclosed at column 3 lines 35-50 of U.S. Pat. No. 4,184,004.

The dyes useful in the process of the present invention are watersoluble and are classified as direct cotton dyes or direct dyes, as theydye cotton directly; see Venkataraman, The Chemistry of Synthetic Dyes,Vol. 1 p. 271, Academic Press, Inc., New York, 1952. From this class ofdyes one selects a suitable dye, or a group of dyes, that is compatiblewith the unique bioactive compound/rewetter system used in the processof my invention. The selection is made emperically by testing variouscandidate dyes. Suitable dyes include:

    ______________________________________                                        from Atlantic Color and Chemical:                                             Direct Blue NDT   not available                                               Direct Blue 2GR-NB                                                                              C.I. No. Direct Blue 284                                    Direct Blue 2RR-NB                                                                              C.I. No. Direct Blue 283                                    Direct Blue 2RL-NB                                                                              C.I. No. Direct Blue 286                                    Direct Blue 3RR-NB                                                                              C.I. No. Direct Blue 285                                    Direct Blue R-NB  not available                                               from Crompton and Knowles:                                                    Intralite Blue NB-LL                                                                            C.I. Direct Blue 80S                                        Intralite Blue FFC                                                                              C.I. Direct Blue 71                                         from Ciba Geigy:                                                              Solophenyl Blue BL                                                                              C.I. Direct Blue 106                                        ______________________________________                                    

Additionally included in the pad bath is a minor amount of a binder toassist in retaining the dye on the substrate and to provide a measure oflint control. Suitable binders include polyvinyl alcohol or RhoplexHA-16 from Rohm and Haas. The amount of binder is adjusted so as not tomask the reactive sites on the substrate nor to compete strongly withthe antimicrobial agent for the reactive sites on the substrate.

The manner in which the bioactive compound plus hydrophilic couplingagent are placed onto the substrate may be by brushing, spraying orother suitable means known in the textile arts. I prefer to apply therequired components onto the substrate by padding them using a pad bathhaving generally the following ingredients and amounts expressed inweight percent:

    ______________________________________                                                        range    example                                              ______________________________________                                        bioactive compound                                                                              0.2-1.1%   1.0%                                             epoxy-polyoxyalkylene                                                          hydrophilic coupling                                                          agent            0.5-1.5%   1.0%                                             direct dye        up to 1%   0.035-0.35                                       binder                       1.5-4                                            alcohol (solvent) 1-3%       1.0%                                             water             balance    balance                                          ______________________________________                                    

As shown in the above table, the amount of the bioactive compound ispreferably within the range of about 0.2 to about 1.1% calculated on theweight of the solids present in the pad bath. An amount substantiallygreater than 1.1% is difficult to retain on the medical substratewithout leachability difficulties. The alcohol is used to solubilize thehydrophilic coupling agent which is then added to the bioactive compoundto formulate the pad bath.

The pad bath must be applied to the substrate within reasonabletemperature limits, for instance room temperature up to about 35° F.otherwise the bath may become unstable and the pad bath itself willreact with the sides of its container. Accordingly it is appropriate toprepare the pad bath using cold water and to protect the bath fromextreme temperature conditions during storage and operations.

The medical substrate so produced must exhibit an absorptive capacitygenerally in accordance with ASTM D1117 and demonstrate a suitableability to absorb and retain water.

Additionally bleeding is checked by dipping two pieces of the substratein water; placing them on either side of a white blotter paper andpressing then observing the blotter paper for possible bleeding. Theprocedure is repeated using 70% isopropanol or normal silane in place ofthe water.

Applications for the materials produced by the herein described processinclude various medical-type substrates such as non-woven bed coloredcovers and linens, liners and sheets, bandages, dressings, instrumentwraps, instrument tray liners, hospital gowns, caps and garments,surgical drapes as well as many other applications.

What is claimed is:
 1. An absorbent, bioactive, highly wettablenon-woven cellulosic medical substrate having incorporated thereon anon-leachable, bioactive amount of 3-(trimethoxysilyl)-propyloctadecyldimethyl ammonium chloride present in an amount from about 0.15% toabout 1.05% on the basis of the weight of the substrate; as a wettablehydrophilic coupling agent, an organosilicone terpolymer of the formula:##STR3## present in an amount of from about 0.25% to about 1.25% on thebasis of the weight of the substrate; and a tinctorial amount of adirect dyewherein the bioactive material and the hydrophilic couplingagent and the dye are substantively attached to the fibers of thecellulosic substrate, such that the bioactive compound, the hydrophiliccoupling agent and the dye are substantially non-leachable from thesubstrate.
 2. The substrate of claim 1 wherein the amount of bioactivecompound is in the range of about 0.5 to about 1.0%.
 3. The substrate ofclaim 1 or 2 wherein the amount of coupling agent is in the range ofabout 0.5 to about 1.0%.